This application requests five years of continued support for a collaborative, multi-site, interdisciplinary program of research on the neurobiology and genetics of autism and related conditions. In this program of research the investigators propose to study molecular and family genetic factors, brain-behavior relationships, and aspects of developmental course of autism and related conditions. They also propose continued collaboration with colleagues in the CPEA on a number of network-wide collaborative projects. Goals of this program of research includes a) localization of genes in autism through a continued and refined systematic genome search and candidate gene analysis, b) better definition of endophenotypes in autism through analysis of neuropsychological, social, cognitive, and psychiatric profiles of first degree relatives, c) clarification of the neuroanatomical basis of autism through neuroimaging, and 4) examination of issues of stability of phenotypes of autism and prognostic factors through the study longitudinally of cohorts of children with autism and related conditions. In the competitive renewal the investigators seek continued support for four projects and three core resources. Projects include: I) molecular genetics of autism and related conditions, II) family genetics, III) longitudinal studies, and IV) neuroimaging studies. Three core research resources include A) administration and patient recruitment, B) assessment and diagnosis, and C) data management and statistics. This program project builds on the network of existing collaborations and makes use of important resources at each site.